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So I have a Scat Pack with minor bolt ons. I recently ordered Rohana 20x9s for the front of my car and I'm having an issue on the rear size. If I get the 20x10, I can run a 305 555R but is this over kill on the Scat? Would it make more sense to order 2 more 20x9s and put a 275 555R on them? I feel like the bigger rear tires would just be over kill and slow the car down, if anything. Any input on this is greatly appreciated as I'm so torn on what to do.
 

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Lots of people run 315's on their cars. I would not really say its overkill or will slow the car down. 485hp most likely could handle a bigger tire than that.

Ron
 

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Run the 305 or 315 on the back

You wont regret it

Only down side is you cant rotate tires from to back.

More meat on the back looks better and hooks better.
 

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I myself run 555 G2s and have 315s out back mounted on widen WRT wheels (10.5 inch). No issues power wise and love having those wide @$$ tires back there. Looks awesome!



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I myself run 555 G2s and have 315s out back mounted on widen WRT wheels (10.5 inch). No issues power wise and love having those wide @$$ tires back there. Looks awesome!Sent from my iPad using Tapatalk
The 315s on your Challenger look great. I noticed that you are not using mud flaps or 3M protective film on your rear fenders. Have you noticed any problems with paint chipping due to road debris thrown up by the tires? How long have you had them?
 

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So I have a Scat Pack with minor bolt ons. I recently ordered Rohana 20x9s for the front of my car and I'm having an issue on the rear size. If I get the 20x10, I can run a 305 555R but is this over kill on the Scat? Would it make more sense to order 2 more 20x9s and put a 275 555R on them? I feel like the bigger rear tires would just be over kill and slow the car down, if anything. Any input on this is greatly appreciated as I'm so torn on what to do.
The 305s will be fine and look really great on a 20 x 10 wheel. Just make sure that you get a 35 aspect ratio (for correct diameter) and correct wheel offset.

However, if you go to a wider 315 tire, you will need a minimum wheel width of 10.5 for it to wear and perform properly. See link, below.

https://www.1010tires.com/Tools/Tire-Size-Calculator
 

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Discussion Starter #8
Any idea how a 15mm offset 20x10 would work, offset is the depth they in the wheel well correct?
 

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Any idea how a 15mm offset 20x10 would work, offset is the depth they in the wheel well correct?
You need a positive offset wheel. I assume the 20 x 10 wheel, with 15mm offset, is a positive one. I cannot say if this would work because I have the factory 20 x 9 forged aluminum wheels, with 275/40-20 tires. Maybe someone with a 305/35-20 set up can comment.

Here is an excellent tutorial on proper wheel offset.

http://www.wheelpros.com/page/offset-explained/9
 

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First there's no such thing as overkill when your talking tire size in the back. The setups I've run are a little different than what your looking at but here's some info for comparison. I've run a 19x10 with a +20 offset and 285 tire on it and it clears the rear just fine. However if your running a 315 and pinching it slightly on a 10" wheel I suspect you'll need to go to a +15 offset as Cuda said. I currently have a 18x11 on with a 315 and it needs to be a +5 because I have true coilovers in the rear. A buddy who doesn't is able to run a +10 with that wheel/tire. Again not exactly what your looking for but may give you a ballpark to look at.

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So I have a Scat Pack with minor bolt ons. I recently ordered Rohana 20x9s for the front of my car and I'm having an issue on the rear size. If I get the 20x10, I can run a 305 555R but is this over kill on the Scat? Would it make more sense to order 2 more 20x9s and put a 275 555R on them? I feel like the bigger rear tires would just be over kill and slow the car down, if anything. Any input on this is greatly appreciated as I'm so torn on what to do.
Assuming you OEM tires/wheels are 245/45ZR20 9Jx20 ET25.5(ET=offset.) Many have found when putting on 305's with a 25mm offset that they would just make it or would have to remove a a bit of the inner plastic wheel well liner to avoid rubbing. Many after market rim mfgs have been recommending somewhere between 21 and 23mm offset for our cars.

If you're considering 275's you should get at least 9.5" wheels. (You can of course still use the 9" with 275's on the front.) That is the typical design wheel width recommended and would give you the design width of the tire. The industry rule of thumb is that for every 1/2" change in rim width from its "Design Width", the tire's section width will correspondingly change by approximately 2/10".
In fact, if you thought there was a chance you might end up going wider for better hooking in the future, you could get the 10.5" wheels (for the rear) now, giving you the flexibility to mount anywhere from a 275 to a 315 on them.

Sure a heavier, wider wheel would tend to slow a car down a bit, hence the reason for front skinny's at the drag strips. However, I think if you research a bit further that you'll find that the wider tires have been found to improve 0 to 60's and 1/4 mile times on our 485 HP cars.

EDIT: Oh yeah...you can't compare your 0-60 time to someone else with wider tires and think you're getting a good comparison of effect of the wider tires.
 

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Any idea how a 15mm offset 20x10 would work, offset is the depth they in the wheel well correct?
First off...when there is no + or - sign in front of the offset number, it is taken as a + or positive.

15 mm offset would, in effect, move the wheel (assuming your existing offset is 25.5mm) 10.5mm outboard from your car. Now 10.5mm is only .4" (a bit more than 3/8") but with a wider tire you would in effect be moving the outside face of the tire the 3/8" plus half the increase in width between your existing tire and your new tire.
For example, if you currently have 245's (approx. 9.65"wide) and you put on 275's(approx. 10.83") you would be gaining 1.18" in total width. Half that width(since half is inward and half is outwould from the centerline of the tire) is .59 or about 9/16"+.
So in effect you would be ending up with 9/16" + 3/8"(due to offset difference) or roughly 7/8" total that he outside surface of the tire would be moving towards you fender. That may very well still be within your fender in the front. But that is how it works.

So, not that it is, but if your front tire was currently 1/2" inside your fender, it would end up sticking out beyond you fender.

Bottom line...when changing wheel offsets and tire/wheel widths, BOTH the inner clearance as well as the location of the tires outer surface must be kept in mind.
 

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I think the biggest tire I can fit on my SP with the dynamics package is a 305 on the rear. 315's probably won't fit on that stock wheel. Correct?
 

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Discussion Starter #14
I mean on the hell cat fourms alot of people were saying a bigger tire could hurt 0-60 times and that's something that would bother, there are also people running 275 555rs with their stock hellcats that make far greater power than my 392 which is why I'm wondering if there is even a point in going 305 speed wise and the extra rotational mass might slow me down a bit vs a 20x9 rim with a 275 radial
 

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A 315 is definitely too large for a 9.5 rim although some Hellcat fourms member have done it and even some on the 20x9 WR2 wheels have, but the benefits are far less than on a larger wheel.
 

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Discussion Starter #16
I thin other definitely is suck thing as over kill if a 305 is more traction than I need and I buy a 20x10 rim versus a 20x9 and run a bigger tire my rotational mass is going to be far greater and I'll need more power to move the tires, this is why I'm trying to collect data on people who have run with a 275 radial vs a 305 since the heavy 305 on a 20x10 may be pointless if a 275 radial is fine
 

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I just want better grip... These Pirelli's suck the big one. I can't hook at all, and around some corners they are downright dangerous. Although Track mode is pretty good about keeping you safe.
 

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I think the biggest tire I can fit on my SP with the dynamics package is a 305 on the rear. 315's probably won't fit on that stock wheel. Correct?
There's a difference between the widest tire you CAN put on a wheel and the widest tire you SHOULD put on a wheel.
Personally, I would want to stay within the recommended wheel size based on the specific tire manufacturers recommendations. You may find charts that are generalized and that will be different then the tire manufacturers recommendation.
If you are talking a 9" wheel, TYPICALLY the widest tire would be 275. Some have done wider, but typically not recommended unless the tire manufacturer says otherwise.
I wouldn't even go by what some of the vendors say as they have ulterior motives.

Not to confuse the issue but recommended wheel width changes not only with the tire width but also with the tire profile.
A wheel that is too narrow in relation to the tire width will allow the tire to distort excessively sideways under fast cornering. This is part of the reason why you'll see that a higher profile tire sometimes allows a smaller wheel width.
 

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The 315s on your Challenger look great. I noticed that you are not using mud flaps or 3M protective film on your rear fenders. Have you noticed any problems with paint chipping due to road debris thrown up by the tires? How long have you had them?


I’ve had the wider tires for two years now. No I don’t have any means of protection. Reason being is the rear quarter was already marked up so I didn’t bother. I haven’t noticed an increase since adding wider tires either. At least nothing noticeable. I figure that with all the other dings and scratches this thing has accumulated over the years I will just get it repainted or possibly wrapped. I really want to see it in matte black. Thanks by the way!


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What are your 0-60 times on the 315 555 G2

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[/QUOTE]



To be honest no clue.... I’ve never bother to check my 0-60 and I don’t go to the drag strip. I prefer corners and enjoy cruising with the family. I’ll give it a try this weekend if the weather cooperates and report back.


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